DEVICES AND METHODS FOR PROTECTING LASER DIODES FROM ELECTROSTATIC DISCHARGE
In accordance with certain embodiments, an apparatus has a depletion-mode transistor electrically connected to a laser diode. The transistor provides a low impedance path for diverting electrostatic current away from the laser diode. In accordance with certain embodiments, a method for protecting a laser diode from an electrostatic charge includes providing a transistor that is electrically connected to a laser diode and has a drain and a source. The method further includes redirecting the electrostatic charge through a low impedance path from the drain to the source during a powered-on state.
1 . An apparatus comprising:
a depletion-mode transistor electrically connected to a laser diode, the depletion-mode transistor providing a low impedance path for diverting electrostatic current away from the laser diode while the apparatus is powered-on.
2 . The apparatus of claim 1 , further comprising:
a gate driver for controlling an input voltage to a transistor gate; and
a recording head selection input signal in electrical communication with the transistor gate driver, the recording head selection input signal communicating either a selected head state or an unselected head state;
wherein the transistor is configured as an open switch during a powered-on, selected head state.
3 . The apparatus of claim 2 , wherein a laser diode anode is electrically connected to a positive rail.
4 . The apparatus of claim 2 , wherein a laser diode anode is grounded.
5 . The apparatus of claim 2 , further comprising:
a differential circuit electrically connected across the laser diode.
6 . The apparatus of claim 1 , wherein the depletion-mode transistor is an N-type metal-oxide-semiconductor.
7 . The apparatus of claim 1 , wherein the depletion-mode transistor is a P-type metal-oxide-semiconductor.
8 . The apparatus of claim 1 , wherein the low impedance path is between a transistor drain and a transistor source.
9 . The apparatus of claim 1 , further comprising:
at least two transistors electrically connected in parallel.
10 . The apparatus of claim 1 , wherein the apparatus is a storage device.
11 . A method for protecting a laser diode from an electrostatic charge, the method comprising:
providing a transistor electrically connected to a laser diode, the transistor having a drain and a source; and
redirecting the electrostatic charge through a low impedance path from the drain to the source during a powered-on state.
12 . The method of claim 11 , wherein the laser diode is electrically connected to a plurality of transistors connected in parallel.
13 . The method of claim 11 , wherein the transistor is a depletion-mode N-type metal-oxide-semiconductor.
14 . The method of claim 11 , wherein the transistor is a depletion-mode P-type metal-oxide-semiconductor.
15 . The method of claim 11 , wherein the laser diode is utilized in a storage device and the powered-on state comprises a powered-on storage device.
16 . The method of claim 15 , and further comprising:
selecting a recording head of the storage device; and
permitting current to flow through the laser diode when the recording head is selected and the storage device is in the powered-on state.
17 . An electrostatic discharge (ESD) shunting circuit comprising:
a depletion-mode N-type metal-oxide-semiconductor transistor;
a laser diode electrically connected to the laser diode; and
a low impedance path through the transistor from a transistor drain to a transistor source, the low impedance path diverts ESD current away from the laser diode.
18 . The circuit of claim 17 , wherein the circuit is implemented in a rotating storage device.
19 . The circuit of claim 18 , wherein the low impedance path continues to divert ESD current away from the laser diode when the rotating storage device is in a powered-off state.
20 . The method of claim 19 , wherein the low impedance path continues to divert ESD current away from the laser diode when the rotating storage device is in a power-on state.